Circular  No.  1 14. 


v.mlHi 


I  cited  States  hepartment  of  Agriculture, 


BUREAU   OK  XNT 

L.  O.   HOWAKI),    Kutomologit 


THE  EUONYMUS  SCALE. 

matpit  •  uonymi  ( Sotnstock.  |  ° 
By  J.  '•■  Babdem,  M.    \..  Assistant. 
i\n:i » i > i  (  i  in\. 

The  noosl  Berious  enemy  <>!'  the  various  Bpecies  and  varieties  of 
Euonymus  in  the  eastern  United  States  i>  commonly  known  as  the 
Euonymus  scale.     The  injuries  occasioned  by  the  attacks  of  this  pesl 


• .— a  twig  of.  Bnonymni  moderatel;  Infested  with  Boonyi 

almost  preclude  the  growing  of  these  beautiful  plant-  for  hedges  and 
borders,  while  the  dire  experiences  of  some  gardeners  have  caused 
them  to  abandon  entirely  tl><>  use  <iff"tfWe4)l:int-  for  decoration. 

"First  described  in  the  Annual  Report  oJ  jU^^muis'^ micr  . if  .TftnrnUarc  for 
1880,  p.  :r  "  ~-*-~ ■~-^—_ _, 

12607— No.  1 14— 09 


The  attacks  of  this  scale  insect  are  almost  exclusively  confined  to 
Euonymus,  although  it  has  been  found  infesting  the  common  wild 
bittersweet  (  (  'elastrus  scandens),  especially  when  growing'  in  proximit}' 
to  infested  Euonymus.  The  native  wild  species  of  the  latter  plant 
and  the  introduced  and  horticultural  varieties  seem  to  suffer  to  the 
same  extent  from  the  attack  of  their  common  pest,  and  it  is  no 
uncommon  sight  to  see  plants  of  our  wild  species  dying  in  the  open 
forests  and  woodlands. 

In  1886  Lichtenstein  reported  that  at  Montpellier,  France,  this  scale 
was  so  destructive  to  Euonymus  that  it  rendered  the  cultivation  of 
that  plant  almost  impossible;  and  more  recently  from  Japan  come 
reports  of  serious  injury  to  Euonymus  japonica. 

HOST   PLANTS. 

This  insect  was  first  brought  to  the  attention  of  the  scientific  world 
in  the  Agricultural  Report  for  1880  by  Prof.  J.  H.  Comstock,  then 
U.  S.  Entomologist,  who  reported  that  it  had  destroyed  nearly  all  the 
plants  of  Euonymus  latifolia  in  Norfolk,  Va.  There  are  records  of 
its  injury  to  Euonymus  japonica,  E.  europa'us,  E.  radicals,  E.  atro- 
purpureus,  variegated  and  other  horticultural  varieties  of  Euon}rnius, 
and  Cdastrus  scandms  (bittersweet). 

DISTRIBUTION. 

Records  are  at  hand  of  the  occurrence  of  this  scale  in  the  following 
States,  and  it  no  doubt  occurs  in  many  others:  Massachusetts  New 
York,  New  Jersey,  Pennsylvania.  Delaware,  Maiwland,  District  of 
Columbia,  Virginia,  North  Carolina,  South  Carolina,  Georgia,  Ohio, 
and  California.     It  is  also  reported  from  France,  Italy,  and  Japan. 

description. 

This  scale  is  exceedingly  prolific.  A  plant  which  becomes  infested 
is  soon  so  completely-  covered  that  the  attack  results  in  its  early 
destruction.  There  are  at  least  two  broods  each  season,  and  a  prob- 
able third  one  in  the  Southern  States. 

A  badly  infested  plant  appears  as  if  covered  with  snow,  this  condi- 
tion being  due  to  the  presence  of  the  enormous  number  of  the  pure 
white  male  scales,  which  are  more  conspicuous  than  the  brown  female 
scales.  The  photograph  (tig.  l)of  a  moderately  infested  twig  of  varie- 
gated Euonymus  conveys  an  idea  of  the  general  appearance  of  this 
scale.  Note  the  comparatively  few,  elongate-oval,  brown  female  scales 
as  contrasted  with  the  great  number  of  the  narrow,  white,  tricarinate 
scales  of  the  males. 

A-  in  all  the  scale  insects  of  this  class,  the  female  Euonymus  scale 
is  permanently  fixed  to  one  location  except  for  a  few  hours  or  days  in 

[Cir.  114] 


tin-  first  larval  stage,  when  it  appears  :» —  :i  tiny  yellow  object  with  -i\ 
legs  which  are  atrophied  before  if  reaches  the  adull  stage.  The  male 
and  female  larvae  are  similar  in  the  first  stage,  bul  later  the  male 
acquires  a  pair  of  delicate  wings  and  emerges  from  its  scale  covering 
u  free  insect  which  never  feeds,  since  its  mouth-parts  are  replaced  by 
exl ra  ]>:iir-  of  eyes. 

The  following  short  technical  description  with  accompanying  illus- 
tration (fig.  2)  is  appended  for  entomologists  or  persona  who  have 
access  t<>  a  compound  microscope: 


Fro.  2.— Photomicrograph  ol  pygldlnm  of  adult  female  Bnonymiu  - 

jinaJ). 

of  female.  —  I>ark  brown,  with  yellow  exuviae,  of  heavy  texture,  convex, 
broader  posteriorly.  Length,  l.7">  to  2  mm.  Ventral  Bcale  white,  completely  devel- 
oped, attached  to  apper  scale  along  the  sides  bat  free  posteriorly. 

■  of  male. — Pure  white,  parallel  aided,  strongly  tricarinated,   with   yellow 
exuvia.     Length,  l  to  1.25  mm. 

Female.  —  Broadest  at  fifth  pogiuenl  and  tapering  anteriorly  and  posteriorly.  Median 
lobes  and  lobnlee  of  second  and  third  lobes  serrulate  and  pointed,  widely  separated; 
lobules  of  second  and  third  lobes  parted  t>>  the  base,  the  inner  always  the  larger. 
(Hand  spines  comparatively  short  Five  groups  of  paragenital  pores;  median.  4-+>; 
anterior  lateral,  6-9;  posterior  lateral, 


REMEDIES. 


For  the  control  of  t hi-,  pest  two  distincl  treatments  are  available, 
viz.  summer  and  winter  treatment,  each  having  advantages  and  dis- 
advantages.     Arsenical  poisons  (Paris  green,  etc)  are  of  no  avail  in 

[fir.  11J] 


4 


combating  scale  insects  which  suck  the  juices  of  plants;  instead,  a 
corrosive  or  oihr  contact  insecticide  is  necessarily  used. 


SUMMED    TREATMENT. 


All  scale  insects  are  protected  by  waxy  coverings  of  different  kinds, 
except  in  the  young  larval  stage,  in  which  stage  they  are  most  easily 
destroyed  by  insecticides.  The  most  effective  treatment  which  is  least 
injurious  to  the  plant  is  the  use  of  kerosene  emulsion  sprayed  with 
some  force  on  all  parts  of  an  infested  plant  at  the  time  of  the  hatch- 
ing of  the  young,  using  special  care  to  cover  thoroughly  both  sides  of 
all  leaves  and  twigs.  The  time  of  first  hatching  of  the  }'oung  varies 
with  the  seasons  and  latitudes,  and  extends  from  the  first  of  May  to 
the  middle  of  June  in  different  localities.  "Where  no  frost  occurs  the 
dormant  season  is  very  short.  Repeated  thorough  sprayings  of  in- 
fested plants  at  intervals  of  two  weeks  between  the  above  dates  should 
effectively  control  this  scale.  Emulsion  stronger  than  15  per  cent  of 
oil  should  not  be  used  on  plants  during  the  summer,  else  the  foliage 
might  suffer. 

WINTER    TREATMENT. 

During  the  winter  season  plants  are  dormant  and  are  able  to  withstand 
stronger  insecticides  without  injury.  The  deciduous  species  of  Euony- 
mus  should  be  treated  after  the  falling  of  the  leaves,  or  during  winter, 
with  a  25  per  cent  kerosene  emulsion,  or  a  solution  of  whale-oil  soap 
at  the  rate  of  1  pound  to  a  gallon  of  water.  The  evergreen  species 
and  varieties  can  withstand  20  per  cent  kerosene  emulsion  during  tin- 
dormant  season.  Care  should  be  used  to  prevent  the  collection  of  the 
oily  emulsion  at  the  base  of  a  treated  plant,  else  injury  may  result. 

Directions  for  the  preparation  of  kerosene  emulsion  and  the  propor- 
tions of  the  ingredients  are  given  below: 

KEROSENE    EMULSION. 

stuck  Mil i it  inn  (66  per  cent  oil). 

Kerosene  (coal-oil,  lamp-oil) gallons..      2 

Whale-oil  or  1  an  miry  soap  (or  1  quart  soft  soap) pound..       J 

Water gallon. .       1 

Dissolve  the  soap  in  boiling  water,  then  remov<  from  tJu.  ^'/v.add  the 
kerosene  immediately,  and  thoroughly  agitate  the  mixture  until  a  creamy 

solution  is  obtained.  This  can  be  done  by  pouring  the  mixture  into 
the  tank  of  a  spray-pump  and  pumping  the  liquid  through  the  nozzle 
back  into  the  tank.  This  is  a  stock  solution  which  must  be  diluted 
before  using.  In  order  to  make  a  20  per  cent  emulsion,  add  to  each 
gallon  of  the  stock  solution  about  2T'  gallons  of  water  and  agitate  thor- 
oughly before  using.  For  a  25  per  cent  solution  add  to  each  gallon  of 
the  stock  solution  1|  gallons  of  water  and  agitate  thoroughly.  This 
[Cir.  1H] 


strength  will  kill  u  large  percentage  of  the  hibernating  females  with 
«>ut  injury  to  the  plant-. 

[fa  good  naphtha  Boap  can  be  obtained  the  preparation  of  the  emul- 
sion  will  be  simplified.  It  will  he  unnecessary  to  heat  tin'  solution, 
.since  the  kerosene  will  combine  readily  with  the  naphtha  and  soap  and 
form  a  perfect,  >-old,  milk]  -white  emulsion  w  lien  the  mixture  i-  thor- 
oughly agitated.     If  naphtha  soap  is  used,  double  the  amount  called 

for  bj    the  formula,  and  emul-ifv  in  -oft  (rain)  water. 
Approved: 

d  \mi.s  Wilson, 

Secrt  i 'i nj  of  '  JLoricultiirt . 
Washington,  D.  ('..  October  11,  1909. 

[Or.  hi; 


UNIVERSITY  OF  FLORIDA 


3  1262  09216  5272 


7-T. 


